When I was at the EGU meeting in Vienna in April, I attended a session on geoengineering, run by Jason Blackstock. During the session I blogged the main points of Jason’s talk, the key idea of which is that it’s time to start serious research into the feasibility and consequences of geoengineering, because it’s now highly likely we’ll need a plan B, and we’re going to need a much better understanding of what’s involved before we do it. Jason mentioned a brainstorming workshop, and the full report is now available: Climate Engineering Responses to Climate Emergencies. The report is an excellent primer on what we know currently about geoengineering, particularly the risks. It picks out stratospheric aerosols as the most likely intervention (from the point of view of both cost/feasibility, and current knowledge of effectiveness).

But the point made by Jason, and in the report, is that we cannot rule out the likelihood of climate emergencies – either very rapid warming triggered by feedback effects, or sudden onset of unanticipated consequences of (gradual) warming. In other words, changes that occur too rapidly for even the most aggressive mitigation strategies (i.e. emissions reduction) to have an effect on. Geoengineering then can be seen as “buying us time” to allow the mitigation strategies to work – e.g slowing the warming by a decade or so, while we get on and decarbonize our energy supplies.

Finally, along with technical issues of feasibility and risk, the possibility of geoengineering raises major new challenges for world governance. Who gets to decide which geoengineering projects should go ahead, and when, and what will we do about the fact that, by definition, all such projects will have a profound effect on human society, and those effects will be distributed unequally?